1. Field of the Invention
The present invention relates to an apparatus for generating a motor driving control signal capable of being applied to a sensorless motor.
2. Description of the Related Art
Generally, during driving a motor, a speed thereof needs to be controlled to a desired motor driving speed, and in order to control the driving of the motor as described above, the speed of the motor is monitored.
As schemes of monitoring the speed of a motor, there exist a sensor scheme using a sensor such as a hall sensor, an optical sensor, or the like, and a back electromotive force (back EMF) scheme of using back EMF generated in a direction opposite to a direction of rotation of the motor when the motor is rotated, in the case in which a sensor is not used.
Meanwhile, one of existing motor driving methods for driving a motor at a constant speed is to provide an external direct current (DC) input signal. In this method, a signal having a duty ratio of 100% is input from the outside to operate the motor at a maximum duty ratio, that is, at a maximum speed.
In general, minimum and maximum rotation speeds of a motor are determined according to a duty ratio. In the above-mentioned method, for example, the motor is operated at a duty ratio of 100%, that is, at a maximum speed during DC input.
In the motor driving scheme according to the related art as described above, a process of controlling the motor is simple; however, since the DC input signal is provided from the outside, an external signal source is required.
In addition, since the motor is controlled to be rotated only at the minimum or maximum speed, a range of rotation speeds of the motor is significantly limited.
Furthermore, in the case of the scheme using back EMF, since back EMF has a magnitude in proportion to a rotation speed of the motor, it may be very low during initial driving of the motor, such that a feedback control may not be appropriately performed.
The following Related Art Document (Patent Document 1), which relates to a sensorless mode conversion apparatus of a brushless direct current (DC) motor, fails to disclose a technical feature of controlling the driving of a motor in a state in which an initial driving period and a period after the initial driving period are separated from each other.